In this paper, we present an accurate and computationally efficient system-level optical propagation technique suitable for the modeling of optical interfaces. Our technique is based on extensions to the angular spectrum technique used to solve the Rayleigh-Sommerfeld formulation. By using a FFT, the angular spectrum technique is efficient and suitable for system-level modeling of the complete system. To support the reflection and transmission at optical interfaces, we implement a semi-vector technique, taking into account the polarization of the optical wavefront. The polarization is used to determine the reflection and transmission coefficients through the use of Berremans 4x4 matrix. Solutions are provided for typical TE and TM waves, however, wavefronts with arbitrary linear polarization are also supported. In this paper, we present a system-level simulation of a Silicon on Sapphire (SOS) interface.